Jhankwitz- My hat's OFF to you, and with great admiration, recognize that you had the foresight to understand and prototype this RF phenomenon over 60 years ago. Kudos --
I say futuristic because this idea, if it were broadly developed and commercialized, would rock the paradigm of powering wireless communication devices. I realize the losses are a big issue, but the concept of wireless charging was just a dream only a few years ago and now is commercialized. With this, we skip the charging, and go straight to powering. Seems futuristic to me.
Thanks for clarifying that and providing that perspective, 78RPM. Yes, it probably would be a big problem if regular electricity service or RF signals were interrupted, but I agree with your points and think these new energy harvesters are quite ingenius and a good way to leverage existing energy that otherwise would be wasted.
Fair point, jhankwitz, I suppose the potential to use this energy has been around for a long time and, as you point out, people have already been doing it. But I think now it will be utilized more on a larger scale.
Elizabeth, I recall reading the article you wrote. I say we are not stealing if we just take a small amount of radio signal to power a small device. It would probably have gotten reflected and wasted anyway. Now if we were to put up a big antenna array or web to get power, that might rob users in line of sight from getting the signal from the tower.
Regarding electric power lines; if someone just charges a cell phone by capturing the magnetic field from a utility line, I doubt that anybody would notice or care. If 10,000 people did this near the same line, someone would care. I have heard of farmers who laid a half-mile long wire parallel to a power line crossing their property with the purpose of capturing the magnetic flux as AC current. That qualifies as stealing for sure because the magnetic field cannot return to the utility line.
I vaguely recall that a traffic signal in Israel is powered by road vibrations as cars pass over piezo devices. That is not stealing anything as nobody has a vested interest in road vibration.
As an experiment I extended the leads of my Fluke meter in opposuite directions with it set to AC volts. I see abot 5 volts developed across about 20Megohms. That is plenty enough field to make a bug hum in a microphone circuit, but there is not a lot of current available. The same experiment with my 50,000 ohms per volt multimeter shows no meter deflection. So while the potential is there the source impedance is in the tens of megohms. Since the avarage battery has much less than an ohm for internal resistance, it becomes clear that harvesting electrostatic fields will provide micro watts of power, not watts.
There was a project in an issue of Popular Electronics in 1958 called "Stolen Power Radio" and I built one and it worked well. It was 2 AM radios on a single board. the first was a standard 2 transistor AM radio and the second was just the tuner section and a diode rectifier. You would temperarily connect a headphone th the second radio and tune it to the strongest AM station in town and then the rectified signal would power the second radio.
Thanks for this perspective and that information, 78RPM. There really is a lot of potential in energy harvesting, especially for these micro devices. In fact, it's really probably the best application of the technology, given that a lot of them don't need a lot of power and could really be self-sustaining.
It definitely seems like a good solution for these types of situations, Rob. I remember that I did a story about a similar device that harvests energy from ambient electricity sources developed by a German student, and there was a lot of debate about "stealing" the electricity. I didn't really agree with this theory, but I'm wondering if anyone thinks so in this case, too. http://www.designnews.com/author.asp?section_id=1386&doc_id=260486
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